[ExchangeList] Re: IMF config

From: "Jim Harrison" <Jim@xxxxxxxxxxxx>

To: <exchangelist@xxxxxxxxxxxxx>

Date: Fri, 2 Jun 2006 08:39:13 -0700

http://www.msexchange.org
-------------------------------------------------------Unfortunately, that
analogy is flawed.
RDNS isn't "validating the origin"; it's "validating the PTR records in the
netblock owner's DNS server" and nothing else. There are quite a few folks
that can't get a valid PTR record built because their ISP doesn't provide such
a simple service.
The closest thing to your analogy is an SPF TXT record. This uses the DNS
associated with the sending mail domain to determine the validity of the
sending host.
Also keep in mind that unless you're the netblock owner (<giggle> as if any SBS
deployment could be), you can build PTR records in your public DNS all day long
and not affect remote PTR lookups in any way whatsoever.
The only functional way to work around this is via smarthost that actually does
have a valid PTR record.
-------------------------------------------------------
Jim Harrison
MCP(NT4, W2K), A+, Network+, PCG
http://isaserver.org/Jim_Harrison/http://isatools.org
Read the help / books / articles!
-------------------------------------------------------
-----Original Message-----
From: exchangelist-bounce@xxxxxxxxxxxxx
[mailto:exchangelist-bounce@xxxxxxxxxxxxx] On Behalf Of Taylor, George
Sent: Friday, June 02, 2006 08:05
To: exchangelist@xxxxxxxxxxxxx
Subject: [ExchangeList] Re: IMF config
Hmmm, should I dance around like a god? or do they even dance? :-)
I have to disagree with you John. It is standard practice to require a valid
RDNS lookup in order to except a piece of mail. Basically all you are doing is
verifying that the sender is in fact who they say they are, or should I say the
server connecting to your server is who it is advertising itself as. As you
say, take a look at the real world:
A guy walks into your mailroom wearing a purple shirt with a unibomber emblem
and says "Take this package, it's from UPS..." What's your mail clerk going to
say? "I'll take it because I don't care who you are, I just take all packages
addressed to me..."? I hope not, that's how things get blown up, that's how
your email system will get blown up with viruses, spam, threats, etc... If you
cannot verify the origin of a piece of mail and you except it anyways, you put
yourself at risk, a conscience email administrator is not going to allow that.
Just my .02
George Taylor
Systems Programmer
Regional Health Inc.
________________________________
From: John T (Lists) [mailto:johnlist@xxxxxxxxxxxxxxxxxxx]
Sent: Thursday, June 01, 2006 5:07 PM
To: exchangelist@xxxxxxxxxxxxx
Subject: [ExchangeList] Re: IMF config
Andrew, please tell me you are not actually considering doing this.
Yes, the big want-to-be Internet God's such as America Off Line block/refuse on
no PTR, but that is not practical in the real world as the rest of us know it.
Besides, I think America Off Line is just trying to get on Dan Quails' good
side, if he has one.
John T
eServices For You
"Seek, and ye shall find!"
-----Original Message-----
From: exchangelist-bounce@xxxxxxxxxxxxx
[mailto:exchangelist-bounce@xxxxxxxxxxxxx] On Behalf Of Andrew English
Sent: Thursday, June 01, 2006 4:05 AM
To: exchangelist@xxxxxxxxxxxxx
Subject: [ExchangeList] Re: IMF config
Is there anyway to get IMF to drop emails that fail reverse lookup?
Thanks
Andrew
All mail to and from this domain is GFI-scanned.
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